A stack from BatteryStacks is built from Ns*Np
identical cells,
where Np
describes the number of parallel connected cells and Ns
the number of series connected cells.
The parameters of a stack built from Np*Ns
identical cells are calculated as follows:
Description | Cell | Stack |
Nominal OCV | OCVmax | OCVmax*Ns |
End of discharge voltage | OCVmmin | OCVmin*Ns |
Capacity | Qnom | Qnom*Np |
Inner resistance | Ri | Ri*Ns/Np |
The parameters of one cell are summarized in the parameter record cellData.
Dependency of OCV on SOC can be chosen either linear (useLinearSOCDependency=true
) or based on a look-up table.
By default, a linear OCV versus SOC characteristic is defined (like a capacitor), i.e. OCV_SOC[:,2]=[SOCmin,OCVmin/OCVmax; SOCmax,1]
.
The OCV versus SOC table has to be specified with 1st column = SOC values in ascending order, 2nd column = corresponding OCV values with respect to OCVmax.
Be careful using parameter smoothness
for table interpolation, check the resulting characteristic.
Further dependencies of OVC (e.g. on temperature) are not taken into account, this would require a 2-dimensional table look-up.
Self-discharge is specified as discharge current Idis
at SOC = SOCmax
. From that values, a self-discharge conductance is calculated.
If self-discharge should be neglected, set Idis=0
.
Linear temperature dependency of inner resistance can be specified by reference temperature T_ref
and temperature coefficient alpha
:
R = R_ref*(1 + alpha*(T - T_ref))
.
The parameter record for one cell of a transient battery model cellData extends from the basic cellData record, and adds the parameters of the additional RC-elements. These are specified by an array of parameter records rcData:
R
.. Resistance of RC-elementC
.. Capacitance of RC-element
The size of the array rcData has to be defined as parameter nRC
.
The parameters of these RC-elements are results of sophisticated measurements, e.g. cell impedance spectroscopy.
Temperature dependency of the resistors is assumed to be the same as inner resistance Ri
.
End of charge voltage | 4.2 V | |
Nominal voltage | 3.6 V | |
End of discharge voltage | OCVmmin | 2.5 V |
Capacity (i.e. nominal charge) Qnom
, inner resistance Ri
and short-circuit current Isc
depend on the cell size.
Typical (estimated) values for a certain cell size are, as an example:
Capacity | Qnom | 5 A.h |
Inner resistance | Ri | 3 mΩ |
Self-discharge rate is typically 1%/month.
Ns
x Np
cells:
A stack from BatteryStacksWithSensors is built from Ns*Np
cells
arranged in a matrix, where Np
describes the number of parallel connected cells and Ns
the number of series connected cells.
The parameters of such a stack are summarized in the parameter record stackData.
Here the matrix of Ns
x Np
cell parameters records is compiled.
The parameters of original cell data are propagated to all cells except those
whose indices are specified in the array kDegraded[:,2]
. For these degraded cells the parameters of
degraded cell data are propagated.
Note: Any members of the parameter array kDegraded[:,2]
outside the range 1≤kDegraded[:,1]≤Ns
and 1≤kDegraded[:,2]≤Np
are ignored.